Java使用线程池实现socket编程的方法详解

简介

Java中的线程池是用来管理和复用线程的工具。线程池可以减少线程的创建和销毁，节省了系统资源。在socket编程中，线程池可以避免创建大量的线程，优化程序性能。

线程池的实现

线程池的创建可以使用Java中的Executor或ExecutorService接口。这两个类都是Executor框架的一部分，提供了管理线程池和执行线程任务的方法。

下面是一个创建线程池的示例代码：

ExecutorService executor = Executors.newFixedThreadPool(10);

创建的是一个固定大小的线程池，大小为10。根据实际需求，也可以创建单线程池、缓存线程池和可变尺寸线程池。

socket编程与线程池的结合

下面是一个简单的socket编程示例，接收客户端请求并返回信息：

public class Server {
    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = new ServerSocket(8888);
        System.out.println("服务端启动完成，等待客户端请求...");
        while (true) {
            Socket socket = serverSocket.accept();
            System.out.println("接收到客户端请求：" + socket.getInetAddress().getHostAddress() + ":" + socket.getPort());
            InputStream inputStream = socket.getInputStream();
            byte[] buf = new byte[1024];
            int length = inputStream.read(buf);
            String request = new String(buf, 0, length);
            System.out.println("接收到客户端请求：" + request);
            OutputStream outputStream = socket.getOutputStream();
            outputStream.write("Hello World!".getBytes());
            outputStream.flush();
            outputStream.close();
            inputStream.close();
            socket.close();
        }
    }
}

这是一个简单的服务端代码，使用ServerSocket监听端口8888，接收客户端请求并返回信息。

如果仅使用上面的代码，每当有一个客户端连接上来，就会创建一个新的线程来处理请求。如果客户端请求很频繁，就会导致线程创建和销毁的频繁操作，浪费系统资源。

使用线程池来优化代码，只需要将核心代码包装在Runnable接口中，提交给线程池执行即可，如下：

public class Server {
    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = new ServerSocket(8888);
        System.out.println("服务端启动完成，等待客户端请求...");
        ExecutorService executor = Executors.newFixedThreadPool(10);
        while (true) {
            Socket socket = serverSocket.accept();
            System.out.println("接收到客户端请求：" + socket.getInetAddress().getHostAddress() + ":" + socket.getPort());
            executor.submit(new Handler(socket));
        }
    }
}

class Handler implements Runnable {
    private Socket socket;

    public Handler(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            InputStream inputStream = socket.getInputStream();
            byte[] buf = new byte[1024];
            int length = inputStream.read(buf);
            String request = new String(buf, 0, length);
            System.out.println("接收到客户端请求：" + request);
            OutputStream outputStream = socket.getOutputStream();
            outputStream.write("Hello World!".getBytes());
            outputStream.flush();
            outputStream.close();
            inputStream.close();
            socket.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

上面的代码将核心代码封装到Handler类中，并且通过创建线程池的方式来使用线程池，对客户端请求进行处理。

多线程socket编程示例

下面是一个多线程socket编程的示例，客户端连接成功后，传输文件到服务端：

服务端代码：

public class Server {
    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = new ServerSocket(8888);
        System.out.println("服务端启动完成，等待客户端请求...");
        ExecutorService executor = Executors.newFixedThreadPool(10);
        while (true) {
            Socket socket = serverSocket.accept();
            System.out.println("接收到客户端请求：" + socket.getInetAddress().getHostAddress() + ":" + socket.getPort());
            executor.submit(new Handler(socket));
        }
    }
}

class Handler implements Runnable {
    private Socket socket;

    public Handler(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            InputStream inputStream = socket.getInputStream();
            byte[] buf = new byte[1024];
            int length = inputStream.read(buf);
            String request = new String(buf, 0, length);
            if (request.equalsIgnoreCase("file")) {
                System.out.println("请求传输文件");
                length = inputStream.read(buf);
                String fileName = new String(buf, 0, length);
                System.out.println("文件名：" + fileName);
                OutputStream outputStream = new FileOutputStream(fileName);
                while ((length = inputStream.read(buf)) != -1) {
                    outputStream.write(buf, 0, length);
                }
                System.out.println("传输完成");
                outputStream.close();
            } else {
                System.out.println("接收到客户端请求：" + request);
                OutputStream outputStream = socket.getOutputStream();
                outputStream.write("Hello World!".getBytes());
                outputStream.flush();
                outputStream.close();
            }
            inputStream.close();
            socket.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

客户端代码：

public class Client {
    public static void main(String[] args) throws Exception {
        Socket socket = new Socket("localhost", 8888);
        OutputStream outputStream = socket.getOutputStream();
        Scanner scanner = new Scanner(System.in);
        System.out.println("输入文件名发送文件，否则发送字符串");
        String input = scanner.nextLine();
        if (isFile(input)) {
            outputStream.write("file".getBytes());
            outputStream.flush();
            outputStream.write(input.getBytes());
            outputStream.flush();
            InputStream inputStream = new FileInputStream(input);
            byte[] buf = new byte[1024];
            int length;
            while ((length = inputStream.read(buf)) != -1) {
                outputStream.write(buf, 0, length);
            }
            inputStream.close();
            outputStream.flush();
            outputStream.close();
        } else {
            outputStream.write(input.getBytes());
            outputStream.flush();
            InputStream inputStream = socket.getInputStream();
            byte[] buf = new byte[1024];
            int length = inputStream.read(buf);
            String response = new String(buf, 0, length);
            System.out.println(response);
            inputStream.close();
            outputStream.close();
        }
        socket.close();
    }

    private static boolean isFile(String input) {
        try {
            File file = new File(input);
            if (file.isFile()) {
                return true;
            }
            return false;
        } catch (Exception e) {
            return false;
        }
    }
}

上面的代码中，如果客户端输入的是文件名，则客户端向服务端发送"file"请求，并传输文件到服务端；否则客户端向服务端发送普通字符串请求，服务端返回"Hello World!"。